1. Field of the Invention
The present invention relates to a connector ferrule, and method for using same, for the termination of an optical waveguide. Specifically, the ferrule is of a type which is radially compressible upon the insertion of the ferrule into a connector housing.
2. The Prior Art
Achievement of connectors for axially aligning and mechanically coupling optical waveguides has been hindered by the nonuniform configuration of optical waveguide cables. Typical cables comprise a center waveguide core which is surrounded by optical cladding for deterring the escape of transmitted light signals from the waveguide core. Because the waveguide cladding layer of available cables is not necessarily manufactured concentric about the waveguide core, connectors which align waveguide center cores by referencing off of the clad outer diameter of the waveguide cable are not always effective in achieving certain axial positioning of the waveguide core. Attempts to align waveguide cores directly, by removing the cladding from therearound, have also failed because of performance degradation at the coupling interface due to the exposure of the unclad waveguide portion.
U.S. Pat. No. 3,999,837 teaches a connector for coupling optical waveguide bundles. Pursuant to this approach, a ferrule is taught for collecting the waveguides in a profiled ferrule passageway, and a centering bushing is further proposed for centering the ferrule and waveguide during a polishing step in the terminating procedure. While this approach works well and is well received by the industry, certain shortcomings prevent this connector from representing an ideal solution to the industry's problems. First, by requiring a centering bushing, the cost of manufacture of the resulting connector is increased. Secondly, many cables are configured having clad waveguide center cores, and this connector approach is illsuited for termination of such a cable. U.S. Pat. No. 4,186,999 teaches a ferrule having a profiled passageway extending therethrough from a cable receiving rearward portion to a forward bore dimensioned to allow an unclad optical fiber to pass therethrough. Plastics material is introduced into the bore and passageway having an index of refraction approximating the index of refraction of the waveguide cladding. The connector so taught achieves centering of the waveguides by critically positioning the bore through a forward nose of the ferrule, and references directly off of the waveguide core itself. While direct referencing is desirable, the substituted plastics material only approximates the cladding of the waveguide, and the discontinuity between the cladding and the index of refraction matching material can still result in an optical loss at the junction. Also, core diameters can vary from cable to cable, so a more universal ferrule approach is desirable.